Fix ValidatorSetFromProto crash on nil proposer in stored state

sei-tendermint/types/light.go

@@ -94,6 +94,9 @@ func (lb *LightBlock) ToProto() (*tmproto.LightBlock, error) {
 		if err != nil {
 			return nil, err
 		}
+		if lbp.ValidatorSet == nil {
+			return nil, ErrValidatorSetEmpty
+		}
 	}
 
 	return lbp, nil

sei-tendermint/types/light_test.go

@@ -88,8 +88,8 @@ func TestLightBlockProtobuf(t *testing.T) {
 	}{
 		{"valid light block", sh, vals, false, false},
 		{"empty signed header", &SignedHeader{}, vals, false, false},
-		{"empty validator set", sh, &ValidatorSet{}, false, true},
-		{"empty light block", &SignedHeader{}, &ValidatorSet{}, false, true},
+		{"empty validator set", sh, &ValidatorSet{}, true, true},
+		{"empty light block", &SignedHeader{}, &ValidatorSet{}, true, true},
 	}
 
 	for _, tc := range testCases {

sei-tendermint/types/validator_set.go

@@ -811,7 +811,7 @@ func (valz ValidatorsByAddress) Swap(i, j int) {
 // ToProto converts ValidatorSet to protobuf
 func (vals *ValidatorSet) ToProto() (*tmproto.ValidatorSet, error) {
 	if vals.IsNilOrEmpty() {
-		return &tmproto.ValidatorSet{}, nil // validator set should never be nil
+		return nil, nil
 	}
 
 	vp := new(tmproto.ValidatorSet)
@@ -857,13 +857,16 @@ func ValidatorSetFromProto(vp *tmproto.ValidatorSet) (*ValidatorSet, error) {
 	}
 	vals.Validators = valsProto
 
-	p, err := ValidatorFromProto(vp.GetProposer())
-	if err != nil {
-		return nil, fmt.Errorf("fromProto: validatorSet proposer error: %w", err)
+	if vp.GetProposer() != nil {
+		p, err := ValidatorFromProto(vp.GetProposer())
+		if err != nil {
+			return nil, fmt.Errorf("fromProto: validatorSet proposer error: %w", err)
+		}
+		vals.Proposer = p
+	} else if len(vals.Validators) > 0 {
+		vals.Proposer = vals.findProposer()
 	}
 
-	vals.Proposer = p
-
 	// NOTE: We can't trust the total voting power given to us by other peers. If someone were to
 	// inject a non-zeo value that wasn't the correct voting power we could assume a wrong total
 	// power hence we need to recompute it.

sei-tendermint/types/validator_set_test.go

@@ -1459,6 +1459,56 @@ func TestValidatorSetProtoBuf(t *testing.T) {
 	}
 }
 
+func TestValidatorSetFromProto_NilProposerWithValidators(t *testing.T) {
+	pk1 := ed25519.GenerateSecretKey().Public()
+	pk2 := ed25519.GenerateSecretKey().Public()
+
+	protoValSet := &tmproto.ValidatorSet{
+		Validators: []*tmproto.Validator{
+			{
+				Address:          pk1.Address(),
+				PubKey:           crypto.PubKeyToProto(pk1),
+				VotingPower:      50,
+				ProposerPriority: 10,
+			},
+			{
+				Address:          pk2.Address(),
+				PubKey:           crypto.PubKeyToProto(pk2),
+				VotingPower:      50,
+				ProposerPriority: -10,
+			},
+		},
+		Proposer: nil,
+	}
+
+	valSet, err := ValidatorSetFromProto(protoValSet)
+	require.NoError(t, err)
+	require.NotNil(t, valSet.Proposer, "proposer should be derived when nil in proto")
+	require.Len(t, valSet.Validators, 2)
+
+	found := false
+	for _, v := range valSet.Validators {
+		if bytes.Equal(v.Address, valSet.Proposer.Address) {
+			found = true
+			break
+		}
+	}
+	require.True(t, found, "derived proposer must be a member of the validator set")
+
+	require.Equal(t, valSet.Proposer.Address, pk1.Address(),
+		"proposer should be the validator with highest ProposerPriority")
+}
+
+func TestValidatorSetFromProto_EmptyProtoRoundtrip(t *testing.T) {
+	empty := &ValidatorSet{}
+	proto, err := empty.ToProto()
+	require.NoError(t, err)
+	require.Nil(t, proto, "ToProto on empty set should return nil")
+
+	_, err = ValidatorSetFromProto(proto)
+	require.Error(t, err, "FromProto(nil) should return error")
+}
+
 // ---------------------
 // Sort validators by priority and address
 type validatorsByPriority []*Validator